GB2251537A - Mowers - Google Patents

Abstract

A boom mower has a first arm (10) pivoted to the tractor, a second arm (12) pivoted to the end of the fist arm (10) and forming a guide (12), a pinion (106) in the guide, and a rack (104) displaceable through the guide (12) and carrying a cutting head (16) at its free end, so that the reach of the cutting head (16) on the tractor may be extended by use of the rack (104) and pinion (106).

Description

MOWERS Patent No. GB 2,129,265 shows a boom mower having two arms pivoted end-to-end between a tractor and a cutting head, with three hydraulic rams or like controlling the relative angles for reach, height1 and ground slope Similar mowers have included an extra ram in the second arm with the head carried on the extensible portion of the ram to give reach extension over and above what would otherwise be available.

Even with the added ram, there are limits to the reach which is conveniently usable. Mowers with particularly long arms have been made, for example for motorway embankment use, but have been found ungainly and disadvantageous elsewhere. For example in the stowed position, the height of the folded-up arms which form an inverted Vee shape creates difficulty with low bridges, and if the tractor is to drive along the hard shoulder of a motorway or on the verge adjacent the hard shoulder, it may have to pass below motorway bridges at a point where the clearance is relatively small.

U.S.P.3,462,925 has a single arm which is displaceable axially by a rack and pinion through a housing pivoted about a vertical axis and about a horizontal axis. One ram controls the slew angle about the vertical axis, and a second ram controls the height by tilt (in see-saw fashion) about the horizontal axis.

A third controls the cutter head angle at the end of the arm, and the rack and pinion controls the reach. This arrangement is disadvantageous because of the high centre of gravity necessary. The pivot centre cannot be lowered because the boom extends across the tractor and may need to sweep above the drivers head or cab of the tractor.

Stability may be a problem especially if the tractor itself is to be driven across uneven ground.

The object of the invention is to solve the problem of extending reach without affecting stability According to the invention a boom mower has two arms pivoted together and at opposite ends pivoted to a tractor and to a cutting head, with three hydraulic rams or the like controlling the relative angles for reach, height and ground slope, and is characterised in that the arm extending to the cutting head is a rack slidable in or on a guide and displaceable by a pinion, the assembly of guide and rack being pivoted to the other arm.

Preferably the boom is mounted on a further pivot at a low point for example at the rear of the tractor, for slewing to a mowing position at either side of the tractor or enabling the boom to extend rearwardly generally in the direction of travel so as to occupy low height whilst passing beneath a low bridge. The result is that the centre of gravity is lowered, and furthermore the reaction to the weight of the extended boom is taken at a low point on the tractor, thus further improving stability.

According to an important feature of the invention the boom slewing angle is substantially in excess of 180 degrees, for example is 210 degrees or 220 degrees, symmetrically about a fore and aft axis of the tractor.

Most preferably the position of the cutting head relative to the boom is controlled by a second rack and pinion for head slewing through about 180 degrees. By these means in combination the mower can cut on the left or right side of the tractor, with the head at extreme positions of reach disposed forwardly of the driver, and even at near positions, the driver will be able to observe the area immediately in front of the mower head, and thus become aware of obstacles, without having to turn his head to face the rear. It is believed that this is a completely novel result in roadside mowers.

Boom slewing (from side-to-side) may be via a third rack and pinion (the boom extension arrangement being the first, and the mowing head slew means the second) hydraulically driven, which allows the so-called break out point to be controlled. If the cutting head meets an obstacle which the driver had not seen, the arms are to pivot about the boom slewing axis. This is called break out, and my be resisted by the hydraulic means effecting the slewing or by a separate hydraulic holding device.

The well known problem here is due to the variable reach of the arms which apply a variable leverage, that is a different physical moment (product of force times distance). If the anti-breakout is set for a particular moment at full reach the arms will not break out at need under except higher loads when at less than that reach.

According to a further feature of the invention, each of the pivots between the tractor, arms and head is associated with a potentiometer providing an electrical signal analogue of angular position, which signals are fed to a microprocessor and compared with a memory to provide an analogue of the reach setting. Different reach settings may be used to control a pressure relief valve or valves in the hydraulic circuit controlling break out. This may allow break out at different moments according to the reach, and actually at the same resistance loads (i.e. when meeting obstacles of the same nature).

The same microprocessor may also be used to allow a single lever control for reach adjustment so as to give effectively straight line movement of the cutting head between inboard and maximum extension.

In ordinary use in positions particularly close to the tractor and at contracted positions of the boom a substantial portion of the rack will extend on the opposite side of the guide to the cutting head. This will also enable the mower to be used for example for siding a high hedge at a position close to the tractor in a manner impossible with known designs.

The cutting head may have any desired cutting means e.g. but without limitation a flail set which conveniently can be hydraulically driven. In addition the cutting head may be angled in known fashion by the third ram and may have cutting height sensing means, all of which together necessitate a plurality of hydraulic hoses, and possibly also electric conductors which are to extend over the (variable) length of the boom Conveniently these hoses and conductors are formed into a bundle laid in a channel in the top of the rack and extending in a loop to a fixed point on the adjacent arm of the boom. As the rack moves to extend the boom the loop will diminish, and vice versa.

The cutting head may be self-propelled. This is of particular value at maximum reach. Conveniently a hydraulic motor is provided on the head to drive a ground contacting roller which trails behind the head for the propulsion purposes, and this motor may be switched in or out, or possibly the drive power varied, according to reach, using the same microprocessor and reach analogue provided from the potentiometers.

One presently preferred embodiment of the invention is now more particularly described with reference to the accompanying drawings wherein: Figure 1 is a somewhat diagrammatic front elevation view showing the cutting head in seven different positions; Figure 2 is a similar view showing the cutting head in four different positions; and Figure 3 is an elevation of the mowing arrangements detached from the tractor.

Turning first to Figure 1, the mower comprises an inner arm 10 pivoted to an outer arm 12 in which rack 14 is guided for sliding movement, with a cutting head 16 at the end of the boom which comprises parts 10-14. In the illustration bearing the mentioned reference numbers, the cutting head is in a substantially vertical position as used for siding a hedge The chain dot line 18 shows the arm 10 swung to a lower position, and the rack 14 extended out of the guide 12, possibly to its full extent, and additionally the cutting head turned through about 90 degrees to a mowing position. The chain dot line 20 is similar and here the head is mowing level ground indicated by the chain dot line 22. The chain dot line 24 shows the system lowered still further so as to cut the side of an embankment 26 whilst the tractor rides along the top of the embankment.

The arm can be slewed from side-to-side, as mentioned, and as later herein described, and for cutting on level ground, for example the top of the embankment at 28 close to the tractor the arm occupies the position 100, the guide the position 120 and the rack the position 140. Further, if the terrain is such that bank 30 slopes down to the tractor, this can be coped with by adjusting the position of the cutting head to that shown by the reference 32.

It will be appreciated that these positions are only illustrative, and any position on the left can be duplicated on the right.

Turning now to Figure 2, the typical tractor will comprise cab 40 housing the driver, front wheels 42 and rear wheels 44, and the mower of the present invention is rear-mounted, typically on the power operated links provided at the rear of a tractor for the purpose of carrying implements, or on a rigid mounting e.g. attached to the tractor rear axle, and the so mounted portion or base is indicated by the reference 46. The slewing pivot axis 48, about which the boom swings to turn from left to right is within that base. As mentioned, an important feature of the invention is that slewing occurs through the angle 50 which may be of the order of 220 degrees and the effect of this is clearly illustrated in the figure.

At the full reach position such as 52 or 54 (corresponding to position 32 of Figure 1) the driver can see the whole of the head by a sideways glance without turning his head to the rear. Even in the near position 56, the driver can see the ground immediately in front of the cutting head by a similar glance, so as to recognise the presence of an obstacle in time to take avoiding action.In the prior art, as far as is known, the normal cutting position for a mower arranged to cut either to the left or the right without the apparatus being detached from the tractor and physically moved to the opposite side, which is inconvenient and time wasting is for the mowing head to be on the chain dot line 60. so that for many purposes the driver would have had to turn in his seat to view the cutting head and hence would not be able to control the tractor satisfactorily, except at extremely low speeds of travel This feature of the invention then, providing a slewing angle of 220 degrees, approximately allows for faster movement of the tractor over the ground with the same degree of safety.

Turning now to Figure 3, the base 46 is provided with links 66 for mounting on the tractor, and with a drive shaft 68 for the hydraulic pumps and the like, to be driven from the conventional power take-off shaft of the tractor. A main bracket assembly 70 is pivoted on the slewing axis 48, a pinion (not shown) is mounted relative to that bracket and a hydraulically driven rack drives the bracket and the parts attached to it about the slewing axis, the rack being driven by a hydraulic ram cylinder in a hydraulic circuit and preferably with the anti-break out means as described earlier herein.

The arm 10 is pivoted to the bracket on axis 80 at its inboard end and to the guide 12 about axis 82 at its outboard end. First hydraulic ram 84 is pivoted to the bracket on axis 86 and to the arm 10 on axis 88.

Extension and contraction of this ram 84 lifts and lowers the arm system as a whole.

Arm 10 is connected to guide 12 by second hydraulic ram 90 pivoted to the one part on axis 92 and to a system of swinging links 94 with axes 96 98 102, arranged to ensure that the ram 90 remains generally parallel to the length of the arm 10 even at extreme angles of the guide 12 relative to the arm. The guide is generally tubular, and carries the rack 104 and pinion 106 driven by its own hydraulic motor for displacing the rack in the direction of the arrows A-A relative to the guide 12. Guidance is afforded by corner rollers 108 110 carried by the guide 12 on brackets, and rolling along the corners of the generally U section rack 104.

Third ram 114 extends between a pivot 116 on a bracket carried by the rack 104 and a further system of links 118 for the purpose of angling the cutting head 122 i.e. changing it from the position 16 to the position 32 or 56 for example. The links 118 again prevent the ram fouling on the rack at extremes positions of angle.

A further rack and pinion is provided for slewing the cutting head 122 about the axis 126, that is to turn it about axis 128, so that it may be always in front of the arm whether the arm is to the left or to the right of the tractor: for certain operations e.g. hedge trimming the head may require to be parallel to the tractor, in a mid position between slewing extremes.

The general line followed by the flexible hoses supplying hydraulic fluid to the rams, drive motor for the pinion and the like is shown by the chain dot line 160. These hoses extend in a bundle generally from the base 46 along the arm 10 passing to bulkhead 103 via a slot in the base of the channel section rack 104 into and then lying in that channel to extend through to the cutting head end of the rack 104. Thus the bundle forms a loop, and as the rack 104 moves bodily in the direction A-A in extension or retraction, the loop moves, and the hoses etc unwind from one end of the loop and go into the loop at the other end of the loop.

A further hydraulic motor 166 on the cutting head may be used to drive the cutter shaft per se, and a similar one to drive a ground engaging roller in the cutting head.

Claims (10)

1. A boom mower in which the boom comprises two arms pivoted together and at opposite ends is pivoted to a tractor and to a cutting head, with three hydraulic rams or the like controlling the relative angles for reach, height and ground slope, and characterised in that the arm extending to the cutting head is a rack slidable in or on a guide and displaceable by a pinion, the guide being pivoted to the other arm.

2. A boom mower as claimed in Claim 1 mounted on a further pivot at the rear of the tractor for slewing about a substantially vertical axis between mowing positions at either side of the tractor.

3. A mower as claimed in Claim 2 wherein the slewing angle is substantially in excess of 180 degrees.

4. A mower as claimed in Claim 3 wherein the slewing angle is of the order of 210-220 degrees symmetrically about a fore-and-aft axis of the tractor.

5. A mower as claimed in any preceding claim wherein the cutting head is pivoted for slewing relative to the boom so as to be at least capable of location forwardly of the boom whether the boom is located to the left or right of the tractor.

6. A mower as claimed in claim 5 wherein said cutting head slewing is under the control of a second rack and pinion which is hydraulically actuated.

7. A mower as claimed in any of Claims 2-6 wherein boom slewing is under the control of a third rack and pinion also hydraulically driven.

8. A mower as claimed in claim 7 wherein resistance to movement of the boom away from the slewed position (break out) is hydraulically controlled via at least one release valve.

9. A mower as claimed in Claim 8 wherein potentiometers are provided in joints of the boom system affording an electrical analogue of reach, and a microprocessor is provided utilising the analogue for comparison with a memory and providing signals to operate said release valve according to reach position.

10. A mower as claimed in Claim 1 wherein the rack is guided relative to the guide by corner rollers.